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Mobile Source Emission Inventory -- Categories

This page last updated on December 30, 2014

Category specific emissions estimates have been developed over the past several years in support of specific agency regulatory objectives. Documentation and emissions estimates are available through the regulatory process; this site provides links to available information for each rulemaking.

On-Road Motor Vehicles:

The EMFAC emissions model is developed and used by ARB to assess emissions from on-road vehicles including cars, trucks, and buses in California, and to support ARB's regulatory and air quality planning efforts to meet the Federal Highway Administration's transportation planning requirements.

EMFAC2014(New)

ARB is officially releasing EMFAC2014 to the public on Tuesday, December 30th, 2014. As the latest version of the model, EMFAC2014 represents ARB's current understanding of motor vehicle travel activities and their associated emission levels. Compared to previous versions of EMFAC, there has been a variety of changes to the Graphical User Interface and to the overall flow of using EMFAC. As a result, it is strongly recommended that users thoroughly read the User's Guide before installing and running the model. In addition, ARB will be scheduling training webinars in early 2015 that will provide tutorials on how to use EMFAC2014. Please join the MSEI email list if you would like to be informed of the dates and times of future training webinars as well as general developments related to EMFAC2014.

Over the past 8 years ARB has also developed emissions inventories for regulatory purposes. Historical documentation and methods are posted below. Staff is currently engaged in developing emissions estimates for the Advanced Clean Cars rulemaking.

Off-Road Motor Vehicles:

In the past ARB released the OFFROAD model which calculated emissions from off-road sources. The OFFROAD model is now being replaced by category specific methods and inventory models that are being developed for specific regulatory support projects. The categories listed below have been or are being updated with new methods and data. Where available, new inventories and models are provided. If a category is not listed below, OFFROAD2007 is the current tool for estimating emissions. It is available here.

Off-Road Diesel Equipment:

Note: This version of the inventory model for In-Use Off-Road Equipment is identical to the one developed for the 2010 amendments but with activity, population, and average horsepower fields in the output.

"This revised copy of the 2007 documentation corrects an engine load factor equation that was mis-typed in the original documentation (page 21). This change does not affect the emissions inventory because the correct equation was used for the emissions estimation."